 Free-electron fraction during hydrogen--helium recombination

ID: free-electron-fraction-during-hydrogen-helium-recombination

Codex  0 Created 2026-09-24 Updated 2026-09-24

With singly ionized helium and helium mass fraction

Y_{p}

\frac{n _{e}}{n _{B}} = (1 - Y_{p}) X_{H^{+}} + \frac{Y _{p}}{4} X_{H e^{+}} .

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